Detection rules › Kusto
Cisco Cloud Security - Empty User Agent Detected
'Rule helps to detect empty and unusual user agent indicating web browsing activity by an unusual process other than a web browser.'
MITRE ATT&CK coverage
| Tactic | Techniques |
|---|---|
| Command & Control | T1001.003 Data Obfuscation: Protocol or Service Impersonation |
Rule body kusto
id: 2b328487-162d-4034-b472-59f1d53684a1
name: Cisco Cloud Security - Empty User Agent Detected
description: |
'Rule helps to detect empty and unusual user agent indicating web browsing activity by an unusual process other than a web browser.'
severity: Medium
status: Available
requiredDataConnectors:
- connectorId: CiscoUmbrellaDataConnector
dataTypes:
- Cisco_Umbrella_proxy_CL
queryFrequency: 15m
queryPeriod: 15m
triggerOperator: gt
triggerThreshold: 0
tactics:
- CommandAndControl
relevantTechniques:
- T1001.003
query: |
Cisco_Umbrella
| where EventType == "proxylogs"
| where HttpUserAgentOriginal == ''
| extend Message = "Empty User Agent"
| project TimeGenerated, Message, SrcIpAddr, DstIpAddr, UrlOriginal
entityMappings:
- entityType: URL
fieldMappings:
- identifier: Url
columnName: UrlOriginal
- entityType: IP
fieldMappings:
- identifier: Address
columnName: SrcIpAddr
version: 1.1.3
kind: Scheduled
Stages and Predicates
Stage 1: source
Cisco_Umbrella
Stage 2: where
| where EventType == "proxylogs"
Stage 3: where
| where HttpUserAgentOriginal == ''
Stage 4: extend
| extend Message = "Empty User Agent"
Stage 5: project
| project TimeGenerated, Message, SrcIpAddr, DstIpAddr, UrlOriginal
Indicators
Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.
| Field | Kind | Values |
|---|---|---|
EventType | eq |
|
Output fields
Fields the rule emits when it matches. Chronicle authors list these in the outcome block; they appear on the detection and $risk_score drives alerting. Sentinel / Defender XDR rules build them up through project / summarize / extend stages. Sentinel maps these into alert fields via entityMappings and customDetails; Defender XDR custom detections surface them as alert fields directly.
| Field | Source |
|---|---|
DstIpAddr | project |
Message | project |
SrcIpAddr | project |
TimeGenerated | project |
UrlOriginal | project |